The Glandular Sensory Organ of Desmodoridae (Nematoda)-Ultrastructure and Phylogenetic Implications

Bauer-Nebelsick, Monika; Blumer, Michael; Urbancik, W.; Ott, Jörg

doi:10.2307/3226876

Cited by 37 publications

(20 citation statements)

References 11 publications

(12 reference statements)

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“…Only secretions of the amphid and of the glandular sensory organs, structures known to secrete mucopolysaccharides , Bauer-Nebelsick et al 1995 were labeled. D-galactose and N-acetyl-D-galactosamine were found neither on the bacteria nor on the cuticle of L. cosmopolitus.…”

Section: In Vivo Incubation With Fitc-labeled Lectinsmentioning

confidence: 99%

Attachment mechanism in a highly specific association between ectosymbiotic bacteria and marine nematodes

Nussbaumer¹,

Bright²,

Baranyi³

et al. 2004

Aquat. Microb. Ecol.

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The marine Stilbonematinae (Nematoda) are known for their highly specific mutualistic association with thiotrophic ectosymbiotic bacteria. The mechanism mediating recognition and binding between symbionts and host was studied in 5 host species. When incubated with D-mannose and L-rhamnose the symbionts detached in 2 species, Laxus cosmopolitus and L. oneistus, most likely due to competitive interactions with sugars involved in the binding mechanism; 3 other species, Stilbonema maium, Eubostrichus topiarius and E. dianae, did not lose their bacteria during any tested sugar incubations. Incubations with lectins binding specifically to D-glucose/D-mannose (ConA, concanavalin agglutinin) and to D-mannose (NPA, Narcissus pseudonarcissus agglutinin) respectively, both in vivo and on ultrathin sections, confirmed that accessible D-mannose is located on the symbionts of L. cosmopolitus, but not on the host's surface. Our results showed an involvement of D-mannose and L-rhamnose residues of the bacterial surface in the attachment mechanism. We hypothesize that the recognition and binding of the environmentally transmitted symbionts in the 2 Laxus species, which harbor only 1 phylotype of symbiotic γ-proteobacterium each, is most probably mediated through a yet unknown mannose/rhamnose-specific lectin of host origin.

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Section: In Vivo Incubation With Fitc-labeled Lectinsmentioning

confidence: 99%

Attachment mechanism in a highly specific association between ectosymbiotic bacteria and marine nematodes

Nussbaumer¹,

Bright²,

Baranyi³

et al. 2004

Aquat. Microb. Ecol.

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“…All these setae, including the saw-tooth ones (Fig. 4B), appear to be connected with gland cells ("glandular sensory organs", Bauer-Nebelsick et al 1995). Setae on the tail stronger than the anterior ones, 8 mm long.…”

Section: Description Of a Malementioning

confidence: 99%

Leptonemella species (Desmodoridae, Stilbonematinae), benthic marine nematodes with ectosymbiotic bacteria, from littoral sand of the North Sea island of Sylt: taxonomy and ecological aspects

Riemann

Thiermann

Bock

2003

Helgoland Marine Research

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Leptonemella species represent a dominant element of the nematode fauna in sulfidic, deep sediment layers on the sandy shore of Sylt. Based on collections sampled here in 1991-1999, a taxonomic treatise is presented on the three co-existing species, Leptonemella aphanothecae Gerlach, 1950, the closely related L. vicina sp. nov., and L. gorgo Gerlach, 1950. The high incidence of pseudohermaphrodites in the material, mostly functional females with a male copulatory apparatus, is remarkable. The highest population densities of Leptonemella spp. (up to 73 individuals/10 ml sand) were found near polychaete burrows. Because of the great spatial and temporal variations in the oxygen/sulfide regime of these microhabitats, and because of the strong adhesive capabilities of Leptonemella spp., which can anchor themselves firmly to sand grains using caudal glands, we propose that a hemisessile life strategy is employed by these nematodes to fulfill the metabolic needs of their sulfide-oxidizing ectosymbionts.

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“…The GSOs produce a mucus envelope in which symbionts may be embedded. In each GSO the secretory granules accumulate in the canal and are released onto the cuticle surface through a hollow seta (18,19).There is no evidence of vertical transmission of the symbionts, but even very small juveniles carry a complete microbial coat. Colonization of recently hatched or molted stilbonematids must be a rapid process because field collections rarely yielded nonsymbiotic stilbonematids.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

A New C-Type Lectin Similar to the Human Immunoreceptor DC-SIGN Mediates Symbiont Acquisition by a Marine Nematode

Bulgheresi

Schabussova

Chen

et al. 2006

Appl Environ Microbiol

103

105

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Although thiotrophic symbioses have been intensively studied for the last three decades, nothing is known about the molecular mechanisms of symbiont acquisition. We used the symbiosis between the marine nematode Laxus oneistus and sulfur-oxidizing bacteria to study this process. In this association a monolayer of symbionts covers the whole cuticle of the nematode, except its anterior-most region. Here, we identify a novel Ca 2؉ -dependent mannose-specific lectin that was exclusively secreted onto the posterior, bacterium-associated region of L. oneistus cuticle. A recombinant form of this lectin induced symbiont aggregation in seawater and was able to compete with the native lectin for symbiont binding in vivo. Surprisingly, the carbohydrate recognition domain of this mannose-binding protein was similar both structurally and functionally to a human dendritic cell-specific immunoreceptor. Our results provide a molecular link between bacterial symbionts and host-secreted mucus in a marine symbiosis and suggest conservation in the mechanisms of host-microbe interactions throughout the animal kingdom.Stilbonematinae (Desmodoridae, Chromadoria) (27, 28) are especially abundant in tropical calcareous sands, where an oxidized surface layer overlies a reduced one. In the Belize Barrier Reef, two species, Laxus oneistus and Stilbonema majum, even dominate the nematode fauna of shallow sands. Stilbonematids repeatedly cross the boundary between oxidized and reduced sediment layers and thus represent an ideal substrate for bacteria that require both oxygen and sulfide. The worms, in turn, appear to obtain most of their nutrition by grazing on their symbionts (29).Another peculiar feature of symbiotic marine nematodes is a conspicuous system of glandular sensory organs (GSOs) underlying their cuticle (see Fig. 2D). The GSOs produce a mucus envelope in which symbionts may be embedded. In each GSO the secretory granules accumulate in the canal and are released onto the cuticle surface through a hollow seta (18,19).There is no evidence of vertical transmission of the symbionts, but even very small juveniles carry a complete microbial coat. Colonization of recently hatched or molted stilbonematids must be a rapid process because field collections rarely yielded nonsymbiotic stilbonematids.In L. oneistus, whose bacterial coat is composed of a single phylotype of rod-shaped ␥-Proteobacteria (26, 31, 30), symbiont recruitment must be highly selective. The microbial coat starts with a sharp onset some distance behind the anterior end, and the bacterial rods are aligned perpendicularly to the worm's surface. The absence of symbionts on the anterior region does not correlate with fewer or smaller GSOs or with reduced mucus production.Incubation in D-mannose specifically led to symbiont detachment from nematodes belonging to the genus Laxus but not from S. majum. Furthermore, this monosaccharide was found on the surface of the symbionts, but not on L. oneistus cuticle (22). These data led to the hypothesis that L. oneistus binds its s...

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The Glandular Sensory Organ of Desmodoridae (Nematoda)-Ultrastructure and Phylogenetic Implications

Cited by 37 publications

References 11 publications

Attachment mechanism in a highly specific association between ectosymbiotic bacteria and marine nematodes

Attachment mechanism in a highly specific association between ectosymbiotic bacteria and marine nematodes

Leptonemella species (Desmodoridae, Stilbonematinae), benthic marine nematodes with ectosymbiotic bacteria, from littoral sand of the North Sea island of Sylt: taxonomy and ecological aspects

A New C-Type Lectin Similar to the Human Immunoreceptor DC-SIGN Mediates Symbiont Acquisition by a Marine Nematode

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